41 and 51 would move on thanks to winning the semi's. 71 and 81 get in thanks to getting the most votes from the non-winners. So, yes, this means that one semi might get three entrants while the other, only one.

This encourages voting.

If there is a tie for first, both entrants get in and there is one less wild card.
If there is a tie for the second wild card, eh, let em both in.
And if one semi-final winner still ends up with less votes than a strip that isn't a wild card winner? Eh. Winner is winner. Moves on by default.

The total time to do this would be 15 days. Or, basically, two weeks of normal voting.

Alternatively, we just do the regular 10 strip vote over seven days.

I'm good either way. But I must admit I've come to like the idea of giving the runners up a chance as to give a bit of variety in the final vote.